With shoulders, I can understand holding on to 1 charge to maintain dire frenzy, but why would you hold the 2nd charge when you can use it for the damage, focus gen and bestial wrath cdr? And with thunderslash being active only during Aspect of the wild when we have 10% more crit, this gives us an even higher chance of getting procs, so maintaining dire frenzy during Aspect window is even easier.